This invention relates generally to ignition systems for internal combustion engines and more particularly concerns visual display of the operational efficiency of spark plugs and ignition wires associated with an internal combustion engine for continuous observation by the vehicle operator.
Various types of apparata have been devised for the monitoring of spark plug operation, generally falling into one of two classifications.
The first classification includes apparata intended to be advisory to a vehicle operator, normally by providing light bulb indicia of the operation of the spark plugs by use of a multiplicity of light bulbs, one associated with each spark plug. The current to each light bulb is derived directly from a capacitive or inductive coupling to the ignition wire of its respective spark plug. Since the current in the coupling circuit varies in response to the current in the ignition wire, the light intensity of each bulb is somewhat indicative of the efficiency of its related spark plug and ignition wire. However, due to the rapid variations in ignition wire pulses as well as external sources affecting the magnitude of the current in the coupling circuit, variations in light intensity of such devices is not truly indicative of system efficiency. Therefore, such apparata are generally suitable only for on/off indication rather than efficiency.
The other classification includes apparata devised for diagnostic analysis of ignition systems rather than for operator use. Such devices are designed generally not for light bulb indication but rather for metering or oscillographic representation of the ignition system electrical components. Such systems monitor individual spark plugs with sophisticated equipment far exceeding the needs of most vehicle operators.
It is, therefore, an object of this invention to provide an apparatus useful to visually display the efficiency of the spark plugs and ignition wires of an internal combustion engine to a vehicle operator. Another object of the invention is to provide a visual display for the operator which allows evaluation of individual spark plug efficiency by sequential visual comparison of side-by-side indicia representative of the efficiency of each of the spark plugs of the system. Accordingly, it is an object of the invention to provide simultaneous bar graph displays of all of the spark plugs of the system. It is also an object of the invention to provide a bar graph display which permits calibration of the bar graphs such that the bar graph levels may be coordinated during engine idle when all plugs are operating at maximum efficiency so as to provide a visual point of comparison for the operator.